That a huge challenge in othersise nominally "liberal" spheres such as the skeptical community. Look at the huge backlash against the idea of an "atheism +" movement (meaning adding questions of social justice to the mainstream atheist movements, addressing more concerns than just debunking bigfoot and religions), or the hatred in response to even just the basic statement of: "we could do more to address the concerns of, and recruit the interest of, people of color and other minorities."

What Mills is saying is very easy to respond to defensively, and that's almost instinctive for most of us who have been so ingrained with the status-quo, but it's neccesary to surpress that instinct and actually listen, because UNDERSTANDING these things is the way we can then move forward and avoid the pitfalls CAUSED by what he describes.